Long-Term Evolution (LTE) is a next generation mobile broadband network standard defined by the Third Generation Partnership Project (3GPP). The Orthogonal Frequency Division Multiplexing (OFDM) technology is adopted in the LTE, and technologies such as Multiple Input Multiple Output (MIMO) are also introduced. In addition, the bandwidth of 1.25-20 MHZ can be supported, so that the peak data rate and the system capacity are greatly improved, specifically, the peak rate of 100 Mbit/S for downlink and 50 Mbit/s for uplink is supported under the bandwidth of 20 MHz. A flat network structure enhances the scheduling and the radio resource control efficiency, and shortens the continuous delay.
The MBMS service (MBMS for short) has been supported in the third generation mobile communication system, and an Enhanced Multimedia Broadcast Multicast Service (eMBMS) being constructed in a fourth generation mobile communication LTE system is regarded as a service having a bright application prospect. The implementation manner is that an intelligent terminal having a video function receives a digital audio/video service in the form of broadcast/multicast through a Physical Downlink Multicast Channel (PMCH). As for the implementation of eMBMS and the networking mode thereof, 3GPP protocol standard gives a complete solution.
With the rapid development of Internet and the popularization of large screen terminals with multiple functions, a large number of mobile data multimedia services and various kinds of high bandwidth multimedia services appear, such as video conferences, television broadcasting, video on demand, advertisements, online education, interactive games, on the one hand, this meets the multi-service requirement of a mobile user, and on the other hand, this brings a new service growth point to mobile operators. These mobile data multimedia services require that multiple users can receive the same data at the same and have the features of large data volume, long time of duration, sensitive delay and the like compared with general data traffic.
In order to effectively utilize mobile network resources, 3GPP put forwards the MBMS which is a technology of transmitting data from a data source to multiple target mobile terminals so as to share internet (including a core network and an access network) resources and improve the utilization ratio of network resources (in particular to air interface resources). The MBMS defined by 3GPP not only can realize the multicast and broadcast of the message in plain text and low rate, also can improve the broadcast and multicast of a high-speed multimedia service so as to provide a variety of abundant video, audio, and multimedia services, thereby providing a better service prospect for the development of 3G.
User Equipment (UE) for receiving the MBMS can be in one of the two following status: one is a Radio Resource Control (RRC) connected state (RRC_CONNECTED); the other is an RRC idle state (RRC_IDLE). According to the fact that whether the UE is receiving a unicast service, it can be judged that whether the UE which is receiving an MBMS is in the connected state or in the idle state. Specifically, when the UE is receiving the unicast service, the UE is in the connected state. When the UE is in the idle state, an RRC connection is not established between the UE and the network side, and when the UE is in the connected state, an RRC connection is established between the UE and the network side.
If there is an MBMS that UE is receiving in a source cell (also referred to as a current cell), after the UE leaves the source cell and resides in a target cell (if the UE is in the connected mode, the UE can reside in the target cell from the source cell by a handover process, if the UE is in the idle mode, then the UE can reside in the target cell from the source cell through a cell selection/cell reselection process, wherein the above target cell also can be called a new cell), the UE will read messages (wherein an MBMS control signalling which is carried on an MCCH of an MBMS control channel is called as an MCCH message) of a Broadcast Control Channel (BCCH) and a Multicast Control Channel (MCCH) to acquire resource configuration information of the MBMS in the target cell. If the target cell and the source cell belong to the same MBMS over a Single Frequency Network (MBSFN) area, that is, the target cell and the source cell both belong to this MBSFN area (the MBSFN area of the disclosure is also abbreviated as MBSFN), then after entering the target cell, the UE can directly use the MBMS resource configuration information of the source cell (current cell) to receive the MBMS in the target cell without reading the resource configuration information of the MBMS in the target cell, and the contents of the MBMS are carried on the Multicast Traffic Channel (MTCH) of the MBMS to realize the continuity of the MBMS. Each MBMS is carried on one MTCH channel, and each MTCH channel only carries the content of one MBMS, wherein reading an MTCH in the disclosure refers to reading the content of the MBMS carried on the MTCH channel. If the target cell and the source cell belong to different MBSFN areas, then after entering the target cell, UE needs to read resource configuration information of the MBMS. If the MBMS which needs to be received by UE is not sent in the target cell, then after entering the target cell, the UE cannot read the resource configuration information of the MBMS and is also unable to receive the MBMS.
The receiving state of UE having the MBMS capacity includes being receiving an MBMS and being interested in receiving an MBMS. Being interested in receiving an MBMS refers to that UE has not received the MBMS and is prepared to receive the MBMS, under such case, the UE can monitor an MBMS notification message so as to further read the MCCH message and MBMS data according to the MBMS notification message.
Before an MBMS session starts, a Broadcast-Multicast Service Centre (BM-SC) performs service announcement at first, and the purpose of the announcement is to send to the UE a brief introduction of the MBMS, such as an Electric Service Guide (ESG). The announcement can be sent by the following manners: MBMS carrying, or interactive modes, such as Hypertext Transfer Protocol (HTTP), or Picture Transfer Protocol (PTP) push mode, such as SMS, MMS, HTTP push. The announcement may last even after the MBMS session ends. The content of the ESG is carried on a User Service Description (USD), a user can know in advance the MBMS service area (MBMS SA), which is represented by {TMGI, MBMS SAI list} on the USD, of each MBMS service (the MBMS service in the disclosure also may be called a service, or is called MBMS for short) before the service starts by reading the content of the USD carried on the ESG, wherein a Temporary Mobile Group Identity (TMGI) corresponds to a certain MBMS, and the MBMS SAI list corresponds to a Service Area Identity (SAI) list of the service.
In the related art, the process for a user to be interested in a certain MBMS and begin to read the service is described as follows.
The UE knows in advance the TMGI identities corresponding to multiple MBMS including the MBMS of interest, the TMGI identity of which is assumed to be as TMGI1. UE resides in a certain cell, if the user is interested in a certain MBMS (assuming that the TMGI identity of the MBMS of interest is TMGI1), then the UE needs to find and initialize (begin) to read the TMGI1 through the following steps.
Firstly, the UE reads a System Information Block (SIB) of the cell carried on the BCCH. If the UE is interested in a certain MBMS, then the UE needs to read SIB13 (an SIB numbered as 13), configuration information of one or more MCCHs is carried on the SIB13, and each MCCH corresponds to one MBSFN area. By reading SIB13, the UE can read: 1) the MBSFN area ID (MBSFN area identity) corresponding to each MCCH, and 2) configuration parameters of each MCCH (that is, which radio resources on which an MCCH is configured, so as to facilitate the UE to further read an MCCH message correctly on the radio resources).
Then, the UE reads each of the above-mentioned MCCH messages so as to know whether the MBMS of interest is carried in a certain MBSFN area. Each MCCH message carries MBSFN resources configured for the one MBSFN area corresponding to the MCCH message and scheduling information of all MBMSs of the MBSFN area (UE can know which MBSFN resources each MBMS is particularly scheduled on). Each MBMS uniquely corresponds to one MTCH, that is, the content of each MBMS is uniquely carried on one MTCH. Specifically, by reading the MCCH message, the UE can read: 1) which radio resources all the MTCHs of the MBSFN area corresponding to the MCCH message are respectively configured on, and 2) which MTCH that the MBMS of interest of the UE is further scheduled on. For example, the MBMS TMGI1 of interest of the UE is configured on a certain MTCH of a certain MBSFN area.
Finally, the UE reads the content on the MTCH (such as MTCH1) corresponding to the service of interest, and meanwhile, the UE needs to continue reading the MCCH message corresponding to the service of interest. Once the resource configuration regarding the MTCH1 on the MCCH message is changed, the UE can continue reading the MTCH1 on the specified radio resources.
In conclusion, in order to find and initialize (begin) to read the TMGI 1, UE needs to read SIB 13 (to acquire the configuration parameters of the MCCH, read MCCH (to find which MTCH the service of interest is carried on) and read the MTCH carrying the service of interest.
In the process of moving, as for UE in the idle state, a cell selection or reselection flow is usually used to enter a target cell; and as for UE in the connected state, a cell switch flow is usually used to enter the target cell. The cell selection or reselection belongs to the mobility of UE under the idle state. The purpose of the cell selection or reselection is to ensure that the UE in the idle state resides in an optimal cell. In a wireless network, the cell selection or reselection is a necessary process mainly due to the reason that the mobility of the UE and the volatility of the wireless environment may cause the fluctuation of the signal strength and the interference level.
One UE resides in a source cell (original cell) and is in the state of being receiving a certain MBMS of interest in this cell. When this UE moves to a target cell from the source cell and resides in the target cell through cell selection/reselection (or cell handover process), according to the fact whether the source cell and the new cell belong to the same MBSFN area, the mobility of the UE can be further classified into the UE moving in the same MBSFN area (also called: Intra-MBSFN area mobility), or the UE moving in different MBSFN areas (also called: Inter-MBSFN area mobility).
After the UE resides in a certain cell of a certain MBSFN area (set as MBSFN1) and can read an MBMS of interest in the cell, the UE moves to a new cell (set as cell2) from the current cell (set as cell1), under such case, the UE will read SIB13 of the new cell so as to know whether the MBSFN area or MBSFN areas is/are changed by comparing the MBSFN area or MBSFN areas of the new cell with that of the source cell, that is, whether cell2 belongs to the original MBSFN1, and whether the UE can continue receiving TMGI1.
On another hand, a certain cell may be in the coverage area of multiple different MBSFN areas, that is, this cell is within the coverage area of overlapped MBSFN areas. For example, cell 1 is in the overlapped coverage area of {MBSFN1, MBSFN2}, cell 2 is in the overlapped coverage area of {MBSFN1, MBSFN3}, as shown in FIG. 1 which is a schematic diagram of the state that UE moves among multiple MBSFN areas according to the related technologies.
In this case, when the UE moves from cell 1 to cell 2, regarding MBSFN1, the UE is moving in the same MBSFN; however, regarding other MBSFN areas, the UE is moving in different MBSFNs. If the MBMS of interest which is being received is carried in the MBSFN1 area, then the UE can receive the service both in cell1 and cell2, but if the MBMS of interest which is being received is carried in MBSFN2, then when moving from cell1 to cell2, the UE may not be able to continue receiving the service in cell2.
In the prior art of 3GPP, it is generally supposed that the MBMSs configured on two adjacent MBSFN areas are different, that is to say, the prior art mainly describes the service continuity (the continuity in the disclosure refers to that whether the UE can receive the same MBMS when the UE moves between two cells) when the UE moves in the same MBSFN area. However, how to ensure the service continuity of UE to receive the same service when the UE moves in different cells among different MBSFNs, especially the solution of how to keep the continuity of the service under the condition that the MBSFN of the target cell cannot carry the MBMS, is not researched and provided. When the UE moves to a cell the corresponding MBSFN of which can not carry the MBMS, the network side is not aware of this situation, therefore, the network side can not guarantee the continuity of the MBMS which results in the interruption of the service and the dissatisfaction of the user.